1. Field of the Invention:
This invention relates to a magnetic recording medium.
2. Description of the Prior Art
In general, a magnetic recording medium is composed of a support having an undercoat and a magnetic recording layer thereon. In certain cases, a graphite-containing layer is formed on the opposite surface of the support to the magnetic recording layer to provide an endless magnetic recording tape. As materials for such magnetic recording media, there are usually employed triacetyl cellulose, diacetyl cellulose, polyethylene terephthalate, and polyvinyl chloride. A standard composition for the magnetic recording layer comprises about 30 to 40% by volume magnetic powders, about 60 to about 70% by volume of a binder, such as polyvinyl acetate, a copolymer of vinyl chloride and vinyl acetate, or an epoxy resin, and suitable additives.
Heretofore, common endless belt magnetic recording tapes, as mentioned above, comprised a magnetic recording layer provided on one side of a film support, and a graphite layer on the opposite side of the support to the magnetic recording layer. The graphite layer was usually formed by applying a graphite powder having a particle size of less that 10.mu. dispersed in a binder. The anti-abrasion properties of these endless tapes depend substantially on the properties of the graphite layer.
Many methods have been suggested to improve the durability of the graphite layer on these endless tapes. A number involve forming projecting patterns on the graphite layer. Endless tapes having an uneven graphite layer provided with dots or a pattern of oblique lines have a fairly long life.
However, since the applications for such endless tapes have expanded, the tapes thus formed were not satisfactory in all instances. Specifically, when the uses of these spread from sound recording to image recording, the anti-abrasion qualities of these graphite layers were insufficient as the running velocity of the tape increased, thus during usage of the tape, localized reduction of the signal (drop cut) tends to develop due to wearing away of the graphite layer. Therefore, it is necessary to improve the durability of the graphite layer.